1. Field of the Invention
This invention relates generally to charging of rechargeable power supplies such as batteries.
2. Description of the State of the Art
Providing an external source of power to a portable device, such as a personal digital assistant (“PDA”), a mobile communication device, a cellular phone, a wireless two-way e-mail communication device, and other types of device, requires design considerations with respect to both the device and the power source. For example, many portable devices provide a power interface for receiving power from a power source, for instance to recharge a battery installed in the device. Charging systems configured for charging rechargeable batteries or other rechargeable power supplies that have been removed from a device are also known. Another known type of charging system is a multiple function charging system configured to charge a power supply whether it is installed in a device or removed from the device.
Multiple function charging systems enabled for connection of more than one power supply at a time generally charge power supplies in a serial fashion. One power supply is typically charged at a time. Although more than one power supply, such as a device with a battery installed and a spare battery, may be connected to the charging system, charging current is applied to only one power supply at any time. As such, known multiple function chargers offer no charging time advantage over charging systems that accept only one power supply at a time. In the above example of a device and a spare battery simultaneously connected to a charging system, the battery inside the device is normally charged first, and only then is the spare battery charged. The total charging time for the device battery and the are battery is substantially the same as the time required to charge each battery separately.